2005 THE MICHIGAN BOTANIST 29 THE VASCULAR FLORAOF HOG ISLAND, CHARLEVOIX COUNTY, MICHIGAN Cathryn Elizabeth Whately Department of Biology Central Michigan University Mt. Pleasant, Michigan 48859 Current address: Department of Biological Sciences Western Michigan University Kalamazoo, Michigan 49008 [email protected] Daniel E. Wujek Edwin E. Leuck II Department of Biology Department of Biology Central Michigan University Centenary College of Louisiana Mt. Pleasant, Michigan 48859 Shreveport, Louisiana 71104 [email protected] [email protected] ABSTRACT The vascular flora of Hog Island, the fourth largest island of the Beaver Island Archipelago, was inventoried. Up to now, some vascular plants have been collected on Beaver Island, but few speci- mens have been collected from the surrounding islands of the Beaver Island Archipelago. A Floris- tic Quality Index (FQI) value of 92.7 was calculated, indicating that the island is representative of Michigan’s pre-settlement flora. Three hundred and forty species, representing 77 families and 213 genera were collected over three field seasons (2000–2002) with collecting trips made in the spring, summer, and fall. These data were compared to data previously published for the Beaver Island Archipelago. Seventy-three percent of the plant families, 60.5% of the genera, and 43.4% of the species found on the Beaver Island Archipelago as a whole were also found on Hog Island. Among the collections were the threatened species Cirsium pitcheri, Iris lacustris, and Tanacetum huro- nense; Cypripedium arientinum, a plant of special concern; and the endangered Amerorchis rotundi- folia. Seventeen species not previously recorded for the Beaver Island group were documented. INTRODUCTION Michigan has a diverse flora (Voss 1972; 1985; 1996). Much of that diversity is found on the islands of Lake Michigan (Penskar et al. 1999). This diversity is reflected in the floras of the Fox Islands (Hazlett et al. 1986; Hazlett 1993), the Manitous (Hazlett & Vande Kopple 1983), and the Grand Traverse Islands (For- zley et al. 1993; Judziewicz 2001). In addition to the inventories, one of the goals of each of the above studies was to identify plants considered to be of special concern, threatened, or endangered either at the state or federal level. Another island group located in Lake Michigan that has been studied is the Beaver Island Archipelago. The Beaver Island group consists of nine islands: Beaver, Garden, High, Hog, Gull, Trout, Whiskey, Squaw, and Hat. This island group is approximately 30 kilometers west of Emmet County in northern Lake 30 THE MICHIGAN BOTANIST Vol. 44 Michigan, but all of the islands are attached administratively to Charlevoix County. Conifers and flowering plants have been collected from Beaver, Garden, and High Islands. Some of the results of these collections have been published (Voss 1972; 1985; 1996; Hohn 1977; 1980; Penskar et al. 1999) while others have not. Pteridophytes and their allies have also been observed and inventoried on Beaver Island (Veldman & Wujek 1971). There are published reports of state endangered, threatened, or special con- cern plant species on Beaver and Garden Islands. These plants include Cirsium pitcheri (Pitcher’s thistle, threatened), Iris lacustris (dwarf lake iris, threatened) (Van Kley & Wujek 1993; Wujek 1998), Mimulus michiganensis (Michigan monkey-flower, endangered), Tanacetum huronense (Lake Huron tansy, threat- ened), Pinguicula vulgaris (butterwort, special concern) and Littorella uniflora (American shore-grass, special concern) (Wujek 1998; Penskar et al. 1999). Also found on Beaver Island are Castanea dentata (American chestnut, endangered), Solidago houghtonii (Houghton’s goldenrod, threatened), Calypso bulbosa (ca- lypso, threatened), Drosera ×anglica (sundew, special concern), Cypripedium arietinum (ram’s head lady-slipper, special concern), Listera auriculata (auricled twayblade, special concern) and Carex pallescens (pale sedge, special concern) (Wujek 1998). Natural community surveys were conducted on parts of Beaver and Garden Islands in 1998. Four natural community types were identified and recorded: open dunes, boreal forest, mesic northern forest, and northern fen (Penskar et al. 1999). Hog Island is located approximately eight kilometers northeast of Beaver Is- land and is part of the Beaver Island Wildlife Research Area, managed by the Michigan Department of Natural Resources. Except for selective logging in the 1950s (P. Gregg, personal communication), Hog Island remains an undeveloped island that has remained relatively undisturbed by man since the arrival of Euro- peans, making it useful as a baseline for the ecology of the area (Michigan Nat- ural Features Inventory [MNFI], unpublished). As a benchmark for the plant ecology of the area, it is important to have a comprehensive floristic inventory. Researchers from MNFI have made brief visits to the island and noted the oc- currence of some threatened and special concern plants, specifically Solidago houghtonii, Iris lacustris, and Cirsium pitcheri, as well as identifying four nat- ural community types, but no comprehensive work has been done (D. Albert, personal communication). In order to generate a comprehensive study of the flora of Hog Island it is important to know what plant species might be expected. The plant species that may be expected in a given area will depend on many fac- tors including the geologic history, and topography of the area, the soil types and plant communities found in the area, and the use of the area by humans. The goal of this study was to complete a comprehensive floristic inventory of Hog Island. Special attention was paid to species that have State of Michigan special concern, threatened, or endangered status and to the variety of exotics found on the island. Using the floristic inventory, a Floristic Quality Index (FQI) value was calculated for Hog Island in order to determine how representative Hog Island is of Michigan’s native biodiversity. 2005 THE MICHIGAN BOTANIST 31 FIGURE 1. Hog Island in relationship to the other islands of the Beaver Island Archipelago and to the state of Michigan. METHODS AND MATERIALS Study Site: Hog Island is the fourth largest island in the Beaver Island Archipelago (Fig. 1), having an area of approximately 10km2, depending on the lake levels. The elevation of the island ranges from 176–187 m above sea level, and it has an undulating topography. (The average high water level of Lake Michigan is 177.1 m.) The highest point on the island is in the central part of the southern half of the island. Hog Island was below lake levels during both the Lake Algonquin and Lake Nipissing stages of the Great Lakes glacial history (Schaetzl 2002). Therefore, Hog Island has only been ex- posed for plant colonization for a maximum of 3200 years. Hog Island’s bedrock is part of the Bois Blanc formation, which is composed of cherty dolomite, dolomitic limestone, and limestone (Landes et al. 1945). The plant communities predicted to be on the island by MNFI were Great Lakes marsh, northern wet meadow, bog, conifer swamp, boreal forest, mesic and dry-mesic forests, and rocky beaches (MNFI, unpublished). Lake Michigan levels have been low the last few years, exposing new shoreline habitat (Center for Operational Oceanographic Products and Services 2003). This exposed habitat would be avail- able for expansion by plant species populations already located on the shore, and for colonization by plant species adapted to disturbed habitats or to those species that had seeds present in the seed bank. Neither Native Americans nor Europeans ever permanently occupied Hog Island; however, Na- tive Americans used the island to a limited extent for agriculture and both Native Americans and early Europeans used the island for fishing and maple syrup production (MNFI 1988). Before planes carried mail from the mainland to Beaver Island, Hog Island was used as a resting area for horse teams and their drivers on the winter mail run over the ice between Beaver Island and Cross Village. Hog Island was selectively logged approximately 50 years ago and bulldozed skid paths were made to move the logs (P. Gregg, personal communication). The island is still used for recreation and for research. As a matter of interest, there are two stories about the origin of Hog Island’s name. The first 32 THE MICHIGAN BOTANIST Vol. 44 states that hogs were put on the island to eat the overabundance of water snakes found on the island. The second story says instead that hogs were placed on the island to forage until butchering time. Ev- idence is lacking to support either story. Methods: Vascular plants were collected from Hog Island in the spring (7–10, 24–25 May 2000; 17 May 2001), summer (7, 16–18 July 2000; 25 June 2002), and fall (19 August 2000; 14 September 2001). In order to obtain as complete an inventory as possible, all plant community types predicted to be found on the island by MNFI were searched during spring, summer, and fall. Angiosperms, except for some trees, were collected in flower or with fruits. Gymnosperms were collected without cones, and pteridophytes and their allies were collected with sporangia when possible. Voucher specimens for all taxa listed below are housed in the Central Michigan University Herbarium (CMC). Nomen- clature generally follows Michigan Flora vol. 1–3 (Voss 1972; 1985; 1996) for gymnosperms, mono- cots, and dicots and Flora of North America vol. 2 Pteridophytes and Gymnosperms (Flora of North America Editorial Committee 1993) for ferns and fern allies. A database of vascular plants reported for the islands of the Beaver Island Archipelago was cre- ated, based on data from Veldman and Wujek (1971) and Voss (1972; 1985; 1996). The numbers of taxa (families, genera, species) found on Hog Island were compared to the numbers of taxa found in the rest of the archipelago. The Floristic Quality Index (FQI) for Hog Island was calculated following the method described in “Floristic Quality Assessment with Wetland Categories and Computer Application Programs for the State of Michigan” (Herman et al.